Magnetic ordering of Au0.92Fe0.08: An ultrasonic investigation

The cusplike peak seen in the low field susceptibility of Au0.92Fe0.08 is suggestive of magnetic ordering at 29 K. Recent measurements1 of the specific heat and entropy on a single crystal between 3 and 50 K do not, however, show a cooperative‐type peak. In an attempt to further understand this discrepancy we have made high resolution measurements of the longitudinal wave sound velocity, which is expected to show a critical anomaly at a magnetic phase transition. Over a frequency range from 5 to 55 MHz and between 4 and 150 K no such anomaly has been observed. These results appear to rule out long range ordering in this alloy. A satisfactory explanation of these phenomena has not yet been made.